Lecture 5-2notes1

Lecture 5-2notes1 - Summary of problems Salt and...

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Unformatted text preview: Summary of problems Salt and water rela+ons Homeosta+s 9/29 Freshwater: simple animals Includes •  Protozoans •  Simple metazoans (hydra, sponge, ciliates) •  Freshwater –  Tends to gain water –  Tends to lose salt •  Marine •  Terrestrial –  Net loss/gain of salt depends on diet –  Tends to lose water –  Tends to lose water –  Tends to gain salt Freshwater: simple animals •  Do not have blood •  Cells bathed directly by external medium •  Problems: πout ≅ 0 πin > 0 because some solutes are necessary for life ⇒ Δπ > 0 Which way does water move? 1 Freshwater: simple •  Problem Contrac+le vacuole: Paramecium large feeder vacuoles small contractile vacuole Constant tendency to swell •  Solu+ons? –  Decrease πi somewhat, but not to = πo –  Pump water out as it comes in: contrac+le vacuole 1.  Feeder vacuoles accumulate water 2.  Transfer water to contrac+le vacuole 3.  Contrac+le vacuole fuses with cell membrane, ejects contents See addi+onal notes under 4 ­3 for more informa+on 1 2 large contractile vacuole small feeder vacuoles Freshwater: simple •  Problem Constant tendency to swell •  Solu+ons? –  Decrease πi somewhat, but not to = πo –  Pump water out as it comes in: contrac+le vacuole –  Other possibili+es? Davenport, Anatomy and Physiology Freshwater metazoans •  Cells bathed in extracellular fluid (ECF) –  Blood plasma –  Lymph –  Hemocoel •  πECF = πcell •  Cell is isosmo+c with ECF 2 Freshwater metazoans •  Cells bathed in ECF •  Cells usually isosmo+c with ECF –  No cellular osmo+c problems –  Problem transferred: regulate blood (ECF) with respect to external medium Freshwater metazoans •  Cells bathed in fluid •  Cells usually isosmo+c with fluid •  Blood tends to –  Gain water –  Lose salt •  Across skin, gut, gas exchange surface •  During excre+on Freshwater metazoans •  Cells bathed in fluid •  Cells usually isosmo+c with fluid •  Blood tends to –  Gain water •  Limit gain: waterproof surfaces •  Counteract –  Excrete large volumes of urine Freshwater metazoans •  Cells bathed in fluid •  Cells usually isosmo+c with fluid •  Blood tends to –  Gain water –  Lose salt •  Minimize loss –  Decrease ion permeability of skin –  Very dilute urine 3 Freshwater metazoans •  Cells bathed in fluid •  Cells usually isosmo+c with fluid •  Blood tends to –  Gain water –  Lose salt Marine protozoa •  Protozoa •  Simple metazoa –  Corals –  Sponges •  Cells bathed directly by seawater •  Minimize loss •  Counteract: Ac+ve uptake of salt: by skin, gas exchange surfaces, gut Marine protozoa •  πout=~1000 mOsmol •  Raise πi to 1000 mOsmol –  Use solute that is not involved in genera+ng membrane poten+al –  Use solute that is not involved in basic metabolism •  Not glucose, fructose, pyruvate, etc. Marine protozoa •  Raise πi with solutes (osmolytes) not involved in genera+ng membrane poten+al or basic metabolism •  See Table 13 ­2, p. 580 ­1, in your text for list. –  Does not dis+nguish between intracellular and extracellular accumula+on –  Protozoa: all intracellular –  Metazoa may accumulate extra ­ or intracellularly 4 Marine protozoa (and metazoa) •  Typical osmolytes –  Poly ­alcohols*: mannitol, glycerol (sweet taste) –  Unusual amino acids or other amines: taurine, glycine ­betaine, methyl amine (“fishy” taste) –  Some normal amino acids: proline, glutamate (umami or “delicious” taste) –  Sulfur ­containing compounds (“ocean” odor) *more than 1  ­C ­OH group; ojen derived from carbohydrates Marine metazoa Marine protozoa •  πin = πout: No osmo+c problem •  Ccellsalt < CSWsalt (except K+) –  Organic solutes contribute to πin –  Must ac+vely secrete salt Marine metazoa •  Cells bathed in fluid (blood) •  Two strategies •  Cells bathed in fluid (blood) •  Two strategies –  Osmoconformer: πblood = πSW –  Osmoconformer: πblood = πSW •  Osmo+c pressure of blood conforms to that of seawater •  Who are osmoconformers? –  Many invertebrates –  Some vertebrates •  Who are osmoconformers? •  Types of osmoconformers –  Invertebrates –  Cyclostomes 5 Marine metazoa •  Cells bathed in fluid (blood) •  Two strategies –  Osmoconformer: πblood = πSW •  Who are osmoconformers? •  Types of osmoconformers –  Ionoconformers: ion composi+on same as seawater –  Ionoregulators »  Regulate ionic levels to be constant, different from SW (typically < SW) »  Keep πblood=πSW with organic solute Marine metazoa •  Cells bathed in fluid (blood) •  Two strategies –  Osmoconformer: πblood = πSW •  Advantage: No problems with osmo+c regula+on •  Disadvantage –  Ojen poorly adapted to changing condi+ons –  Excep+ons must regulate πcell to match changes in πblood with organic osmolytes Marine metazoa •  Cells bathed in fluid (blood) •  Two strategies –  Osmoconformer: πblood = πSW •  Advantage: No problems with osmo+c regula+on •  Disadvantage –  Ojen poorly adapted to changing condi+ons »  Restricted to limited range of salini+es: stenohaline –  Examples: cnidarians, echinoderms, lobster –  Excep+ons: »  Oysters (cf. p. 582 in text) »  Ionoregulators (cf. Rana) Marine metazoa •  Cells bathed in fluid (blood) •  Two strategies –  Osmoconformer: πblood = πSW –  Osmoregulator: Regulate osmo+c pressure so that it is constant, generally less than sea water •  Who? Most vertebrates –  Teleosts (except coelocanth) –  Rep+les –  Mammals 6 Marine metazoa •  Cells bathed in fluid (blood) •  Two strategies –  Osmoconformer: πblood = πSW –  Osmoregulator: πblood constant, < πSW •  Advantage: Blood constant, so easier to move between changing condi+ons Marine metazoa Osmoregulators πblood< πSW Tendency to lose water Prevent: waterproof; small urine volume Compensa+on: drink –  Can adapt to wide range of salini+es: euryhaline •  Disadvantage: Always work to maintain blood different from medium Marine metazoa Osmoregulators πblood< πSW Csaltin<Csaltout: Same as ionoregula+ng osmoconformers Marine metazoa Osmoregulators πblood< πSW Csaltin<Csaltout: Same as ionoregula+ng osmoconformers Tendency to gain salts Across skin, gills, gut Exacerbated by drinking sea water (to compensate for water loss) Prevent: decrease Psalts Compensate: excrete salts 7 Regula+on strategies Regula+on strategies •  Review of stresses and strategies in different marine vertebrates. In all strategies, cells and extracellular fluid (ECF) have same π (∼=RT ΣCsolutes) Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology Fig 13-9; Sherwood Klandorf Yancy, Animal Physiology Regula+on strategies 1 1.  Osmoconforming and ionoconforming •  •  •  Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology Salt in extracellular fluid is similar to that in seawater Salt in cells much less Balance of osmo+c pressure due to organic osmolytes Regula+on strategies 1 2 1.  Osmoconforming and ionoconforming 2.  Osmoconforming and ionoregula+ng •  •  •  πECF = πseawater [salt]ECF < [salt]SW Osmo+c pressures made up with organic solutes Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology 8 Regula+on strategies 1 2 3 1.  Osmoconforming and ionoconforming 2.  Osmoconforming and ionoregula+ng 3.  Osmoregulator •  Not all organisms perfect conformers/regulators –  Perfect osmoregulator π of both ECF and cells is less than SW Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology Regula+on strategies Not all organisms perfect conformers/regulators –  Perfect osmoregulator –  Perfect osmoconformer Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology Regula+on strategies Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology Regula+on strategies Not all organisms perfect conformers/regulators Some organisms regulate over a limited range, and slope may be >0 even within that range. Limits range of salini+es organism can tolerate Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology 9 Regula+on strategies •  Organisms with different strategies. •  Marine vertebrates: preqy good osmo ­ regulators, body fluid ~300 mOsm Fig 13-4c; Sherwood Klandorf Yancy, Animal Physiology Regula+on strategies •  Organisms with different strategies. •  Note: inclusion of terrestrial organisms –  Inappropriate: what is osmolarity of environment? Fig 13-4c; Sherwood Klandorf Yancy, Animal Physiology Terrestrial animals •  Strong tendency to lose water to air •  Solu+ons –  Limit loss •  Waterproof where possible (skin, etc.) •  Bury gas exchange surfaces (lungs, trachea) •  Minimize excretory volume, water content –  Replace: eat, drink 10 ...
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This note was uploaded on 09/16/2011 for the course BIO 203 taught by Professor Loretz during the Fall '09 term at SUNY Buffalo.

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